is a volcano?
is a conical hill or mountain formed by material from the mantle
being forced through an opening or vent in the Earth's crust.
are the main features of a volcano?
are active, dormant and extinct volcanoes?
are found in three states - extinct, dormant and active. An extinct
volcano will never erupt again. A dormant volcano has not erupted
in 2000 years. An active volcano has erupted recently and is likely
to erupt again.
are volcanoes located?
are found along destructive (subducting) (diagram)
plate boundaries, constructive (divergent) (diagram)
plate boundaries and at hot spots in the earth's surface.
is the Ring of Fire?
of Fire' (map)
is a volcanic chain surrounding the Pacific Ocean. It is formed
along a destructive (subducting) plate boundary. The BBC News
Web Site contains an excellent article on the 'Ring
are lahars and pyroclastic flows?
most destructive aspect of volcanoes are lahars and pyroclasic
flows. Lahars are volcanic mudflows created when water (from rain
or meltwater from glaciers) and ash mix. This deadly combination
can have devestating results on the surrounding area. When lahars
settle they can be metres thick and as hard as cement. Lahars
can occur long after a volcanic eruption.
Pyroclastic flows are avalanches containing hot volcanic gases,
ash and volcanic bombs. On steep volcanoes pyroclastic flows can
reach speeds of over 100 miles per hour.
do people live close to volcanoes?
have a wide range of effects on humans. These can be problematic
or beneficial. It is usually the destructive nature of volcanoes
which is more widely documented. However, many people rely on
volcanoes for their everyday survival. Today, many millions of
people live close to volcanoes for this very reason.
live close to volcanoes because Geothermal energy can be harnessed
by using the steam from underground which has been heated by the
Earth's magma. This steam is used to drive turbines in geothermal
power stations to produce electricity for domestic and industrial
use. Countries such as Iceland and New Zealand use this method
of generating electricity.
attract millions of visitors around the world every year. Apart
from the volcano itself, hot springs and geysers can also bring
in the tourists. This creates many jobs for people in the tourism
industry. This includes work in hotels, restaurants and gift shops.
Often locals are also employed as tour guides.
from deep within the earth contains minerals which can be mined
once the lava has cooled. These include gold, silver, diamonds,
copper and zinc, depending on their mineral composition. Often,
mining towns develop around volcanoes.
Volcanic areas often contain some of the most mineral rich soils
in the world. This is ideal for farming. [Lava]
and material from [pyroclastic
flows] are weathered to form nutrient rich soil which can
be cultivated to produce healthy crops and rich harvests.
1980 eruption of Mount St Helens
St Helens is found in the Cascade Range, along the west coast
of Washington State, USA. The volcano is 30,000 years old. This
is young by geological standards. Mount St Helens erupts violently
about once every 3,000 to 4,000 years. The volcano erupted most
recently at 08.32 on 18th May 1980.
1991 eruption of Mount Pinatubo
9 June 1991, Mount
Pinatubo, a volcano in the Zambales Range, 80km (50 miles)
north of Manila, capital of the Philippines, hit the headlines.
It became one of the three largest eruptions in the world in the
20th Century. From the 9 June there were many eruptions (timeline
of events). However, none matched that of 12 June. Ash turned
day into night. The eruption caused the deaths of over 700 people.
200 000 buildings were destroyed. You
can read a Who? What? Where? How? Why? fact file about the